Elliptical Diamond Milling: Kinematics, Force and Tool Wear

Abstract

Machining with diamond tools, whether turning or milling has proven itself as themanufacturing process that produces the highest quality surface finish, with the leastamount of form error in the minimum amount of time. However, due to tool wear and theamount of force generated during conventional machining, diamond tools cannot be usedon carbon containing materials such as steel and brittle materials such as silicates. In anattempt to by-pass the material limitations of diamond machining, a new machiningprocess called vibration assisted machining (VAM) has been developed. VAM involvesoscillating the diamond tool, bringing it into and out of contact with the material in rapidsuccession. VAM can either be 1-dimentional (1D), oscillation in a single direction, or 2-dimensional (2D), a summation of two independent tools motions. Currently, researchefforts are focused on 2D vibration machining, 2D tool motion haven been shown to besuperior to 1D tool motion. Over the past 10 years, 2D VAM with diamond tools hasbeen demonstrated to reduce the amount of machining force and increase tool life whenmachining carbon-containing materials over that of conventional machining processes.However the mechanisms of this improvement have yet to be discovered. This researcheffort is focus on: 1) discovering the fundamental mechanical principals behind theimprovement, force reduction and tool wear, 2) developing a model that predicts thecutting forces and tool contact times, 3) establishes guidelines for the use of vibrationassisted machining and 4) developing an industrial grade 2D VAM servo. The reductionsin tool wear and machining forces are related to the path geometry of the diamond tooland the speed and the depth at which it engages the workpiece. A model has beendeveloped and experimentally verified for 2D VAM which predicts the machining forcesand workpiece / tool contact time if the material properties are known. Along with themodel, a set of charts has been developed for both 1D and 2D VAM that relate the keymachining variables to one another. Lastly, a robust 2D VAM diamond tool servo hasbeen designed.